1. Field of the Invention
The present invention relates to a driver assistance system having a position finding system for locating objects in the surroundings of a vehicle and having at least one assistance function.
2. Description of Related Art
Driver assistance systems which support the driver of a motor vehicle in driving the vehicle and/or warn him/her of dangerous situations, for example, an imminent collision, or automatically initiate measures for avoiding the collision or for mitigating the consequences of the collision are often based on a position finding system, in particular a radar or lidar system, using which objects in the surroundings of the vehicle, in particular other vehicles, may be located. Although the distances and relative velocities of the objects are measurable relatively accurately using such position finding systems, they do not allow a determination, or only allow a very rough determination, of the type of located objects in question. For example, using the radar echo of an object does not generally allow one to tell whether it originates from another vehicle, which requires a certain response of the assistance function, or from a tin can lying on the road, which is irrelevant for the assistance function.
A typical example of such a driver assistance system is an adaptive cruise control (ACC) system which allows the speed of the host vehicle to be regulated in such a way that a vehicle traveling ahead is followed at a reasonable distance. In the Z previously used ACC systems the problem of insufficient object detection has been generally eliminated by ignoring stationary targets, i.e., objects whose relative velocity is approximately equal to that of the host vehicle in absolute value. This is possible, since ACC systems are normally used on superhighways or other major roads, where no stationary obstacles on the road are to be expected. Since stationary objects, or very slow-moving vehicles are not detected in this way, or at least do not trigger a system response, a dangerous situation may arise in special cases such as when approaching the end of a traffic jam.